1. Field of the Invention
The invention relates to a hewing or cutting roll including a central roll part and at least one lateral roll part telescopically extractable in the axial direction of the roll, wherein the central roll part and the extractable roll part have each a connection site for a hydraulic cylinder piston unit.
2. Prior Art
In order to enlarge the cutting width of cutting rolls, it has already been known to provide roll sections telescopically displaceable in the axial direction, which are arranged to be displaceable in the direction of the axis of rotation of the cutting roller and fixable in their respective position.
From U.S. Pat. No. 3,730,593, a hewing machine can be taken, in which lateral roll parts are designed to be displaceable relative to a central roll part in order to adapt the cutting width to the respective requirements. To this end, that configuration comprises a plurality of complex slide guides provided in the region of the cutting roll as well as in the region of the bearing and mounting points of the cutter arm. Telescopically extractable and retractable roll parts of that type require relatively complex drives, and the mounting of the telescopically extractable parts must be realized in a manner so as to allow for their axial displaceability on the one hand, and safeguard the rotationally fast connection with the remaining parts of the roll on the other hand. On account of the required axial displaceability, the rotationally fast connection must exhibit some play, whereby such driving connections are exposed to high wear. A change in the cutting width serves in the first place to enhance the maneuverability of the entire machine and is aimed to avoid impediments by already set walling props or the like when passing narrow curves or narrow track sections.
Known devices of the initially defined kind, in which roll parts are mounted so as to be displaceable in the direction of the axis of rotation of the hewing or cutting roll and connected in a rotationally fast manner with the non-displaceably mounted part, may, for instance, be taken from U.S. Pat. No. 3,614,162. In that device, a cylinder piston unit is provided for extracting the displaceable roll part, whose cylinder is rigidly arranged within the driving shaft for the rotary drive of the cutting rolls and whose piston rod is connected with the extractable roll part. Furthermore, an extractable cutting drum has become known from U.S. Pat. No. 3,695,725, wherein the two concentric drum parts of the extractable roll part embrace the drum of the central roll part. The fixation of the cylinder piston unit for the axial drive of the extractable roll part is realized in a manner similar to that of the configuration according to U.S. Pat. No. 3,614,162.
The known configurations involve the disadvantage of some play occurring between the extractable and the central roll parts on account of the complex mounting of the extractable roll part, which has to allow for the axial displaceability on the one hand, and to ensure the rotationally fast connection with the central roll part on the other hand. That play, which is even further increased by the wear occurring during the operation of the hewing or cutting roll, may possibly cause tilting of the extractable roll part relative to the central roll part and, as a result, even canting of the cylinder piston unit, thus leading to an impairment of the axial displacement drive of the extractable roll part.